Endocrine SystemEndocrine System

Week 8Week 8Dr. Walid DaoudDr. Walid Daoud

A. ProfessorA. Professor

Posterior Pituitary Gland HormonesPosterior Pituitary Gland Hormones

ADH ADH and and oxytocinoxytocin are synthesized by are synthesized by hypothalamic neurons and then hypothalamic neurons and then transported through hypothalamo-transported through hypothalamo-hypophyseal tract to be stored in the hypophyseal tract to be stored in the posterior pituitary galnd until their releaseposterior pituitary galnd until their release..

Antidiuretic Hormone (ADH)Antidiuretic Hormone (ADH)

ADH or vasopressin is formed in supraoptic ADH or vasopressin is formed in supraoptic nuclei of hypothalamusnuclei of hypothalamus..

ActionsActions::

11 - -On kidneys: On kidneys: antidiuretic effectsantidiuretic effects..

22 - -On blood vessels: On blood vessels: pressor effectspressor effects..

33 - -On smooth muscles: On smooth muscles: contractioncontraction..

Regulation of ADH secretionRegulation of ADH secretion11 - -ADH secretion is increased byADH secretion is increased by::

. .Increased osmotic pressure of ECFIncreased osmotic pressure of ECF..

. . Decreased blood volume (hypovolemia)Decreased blood volume (hypovolemia)

. . Stress: pain, cold, traumaStress: pain, cold, trauma..

. . Drugs: morphine and nicotineDrugs: morphine and nicotine..

22 - -ADH secretion is decreased byADH secretion is decreased by::

. .Decreased osmotic pressure of ECFDecreased osmotic pressure of ECF..

. . EthanolEthanol..

. . CortisolCortisol..

Diabetes insipidusDiabetes insipidus

It is caused by deficiency of ADHIt is caused by deficiency of ADH..

--PolyuriaPolyuria..

--PolydepsiaPolydepsia..

--Loss of water-soluble vitaminsLoss of water-soluble vitamins..

OxytocinOxytocin

It is formed in paraventricular nuclie of It is formed in paraventricular nuclie of hypothalamushypothalamus..

ActionsActions::

11 - -Uterine contraction during deliveryUterine contraction during delivery..

22 - -Milk letting actionMilk letting action..

33 - -Mild antidiuretic effectsMild antidiuretic effects..

Thyroid GlandThyroid Gland

In the neck in front of tracheaIn the neck in front of trachea..

22 lobes connected by isthmuslobes connected by isthmus..

. .Tri-iodothyronine (T3)Tri-iodothyronine (T3)

. . Tetra-iodothyronine (T4)Tetra-iodothyronine (T4)

. . ThyrocalcitoninThyrocalcitonin

Actions of Thyroid HormonesActions of Thyroid Hormones11--Calorigenic effect:Calorigenic effect: increased metabolic increased metabolic

activity in all tissuesactivity in all tissues..22--Effects secondary to calorigenesisEffects secondary to calorigenesis::

. .On GIT:On GIT: increased activities increased activities.. . .On metabolism:On metabolism: Increased Increased..

. .On basal metabolic rate:On basal metabolic rate: increased BMR increased BMR.. . .On respiration:On respiration: increased rate and depth increased rate and depth..

. .On CVS:On CVS: increased flow, COP and HR increased flow, COP and HR.. . .On CNS:On CNS: Increased reactivity of synapses Increased reactivity of synapses

. .On muscles:On muscles: increased reaction increased reaction..

Actions of Thyroid HormonesActions of Thyroid Hormones

33--Effects on growthEffects on growth::

. . Physical growth: Physical growth: increase linear growth inincrease linear growth in

childrenchildren..

. . Mental growth: Mental growth: brain development in thebrain development in the

first few tears of lifefirst few tears of life..

. . Sexual development: Sexual development: secretion of gonadalsecretion of gonadal

hormones and sexual maturationhormones and sexual maturation..

Regulation of Thyroid HormonesRegulation of Thyroid Hormones

11--TRH from hypothalamus increases TSHTRH from hypothalamus increases TSH..

22--TSH from anterior pituitary gland increasesTSH from anterior pituitary gland increases

synthesis and secretion of thyroid hormonessynthesis and secretion of thyroid hormones..

33--Cold increases TRH secretionCold increases TRH secretion..

44--Emotional stress increases TRH secretionEmotional stress increases TRH secretion..

55--Feedback inhibition:Feedback inhibition: decreased T3 and T4 decreased T3 and T4

cause increased TSH and TRH secretioncause increased TSH and TRH secretion..

HypothyroidismHypothyroidism

In adults: MyxoedemaIn adults: Myxoedema::11--Low BMR (-40%)Low BMR (-40%)..

22--Accumulation of fluid containing proteinsAccumulation of fluid containing proteins under skin (myxoedematous tissues)under skin (myxoedematous tissues)..

33--Decreased heart rate and cardiac outputDecreased heart rate and cardiac output..44--ConstipationConstipation..

55--Slow mentation and sleepinessSlow mentation and sleepiness..66--SterilitySterility..

HypothyroidismHypothyroidismSince birth: CretinismSince birth: Cretinism::

- -Deficiency of thyroid hormone since birthDeficiency of thyroid hormone since birth - -Delay developmentDelay development..

- -Distorted bone and muscle growthDistorted bone and muscle growth -. -. - -Dwarf with mental retardationDwarf with mental retardation..

- -Deficient sexual maturationDeficient sexual maturation.. - -Depressed bridge of nose with wide nostrilDepressed bridge of nose with wide nostril..

- -Protruding tongue, thick lipsProtruding tongue, thick lips.. - -Protuberant abdomenProtuberant abdomen..

Hyperthyoidisn (Throtoxicosis)Hyperthyoidisn (Throtoxicosis)

Exophthalmic goitre; autoimmune disease, Exophthalmic goitre; autoimmune disease, TSH receptor-stimulating antibodies TSH receptor-stimulating antibodies increase T3 and T4 causing exophthalmosincrease T3 and T4 causing exophthalmos

- -Increased BMR. Warm skin, can notIncreased BMR. Warm skin, can not

tolerate heattolerate heat..

- -Tremors, irritability, insomnia andTremors, irritability, insomnia and

exaggerated tendon jerkexaggerated tendon jerk..

- -Loss of weight in spite of ↑ food intakeLoss of weight in spite of ↑ food intake . .

- -Increased heart rate, COP and diarrheaIncreased heart rate, COP and diarrhea..

Calcium HomeostasisCalcium Homeostasis

Functions of calciumFunctions of calcium::

- -Mineralization of bone and teethMineralization of bone and teeth..

- -Blood clottingBlood clotting..

- -Release of neurotransmittersRelease of neurotransmitters..

- -Neuromuscular excitabilityNeuromuscular excitability..

- -Muscle contraction and relaxationMuscle contraction and relaxation..

- -Hormonal secretion and functionHormonal secretion and function..

Calcium HomeostasisCalcium HomeostasisCalcium BalanceCalcium Balance::

Absorbed calcium passed to ECF which Absorbed calcium passed to ECF which contain 1 gm of calcium, 50% is deposited contain 1 gm of calcium, 50% is deposited daily in bones and absorbed again to pass daily in bones and absorbed again to pass to ECF, so bones are in a continuous to ECF, so bones are in a continuous

turnover and remodelingturnover and remodeling . .

1%1% of bone calcium is (exchangeable Ca), of bone calcium is (exchangeable Ca), providing buffering mechanism to maintain providing buffering mechanism to maintain Ca in ECF constantCa in ECF constant..

Calcium HomeostasisCalcium HomeostasisCalcium balanceCalcium balance::

1010 gms calcium filtered by kidney daily but gms calcium filtered by kidney daily but 98% are reabsorbed in renal tubules and 98% are reabsorbed in renal tubules and only 175 mg are lost in urine daily equal to only 175 mg are lost in urine daily equal to the amount absorbed from GITthe amount absorbed from GIT..

Amounts of calcium lost in urine and feces Amounts of calcium lost in urine and feces vary depending on body needs. There is vary depending on body needs. There is less calcium loss in pregnancy, lactation less calcium loss in pregnancy, lactation and infancyand infancy..

Plasma calciumPlasma calciumNormal plasma calcium 9-11 mg/100 mlNormal plasma calcium 9-11 mg/100 ml::

11 - -50%50% ionized ionized 2- 40% protein-bound (bound to albumin) 2- 40% protein-bound (bound to albumin) 3- 10% complex diffusible calcium bound3- 10% complex diffusible calcium bound

to phosphates, bicarbonates and citratesto phosphates, bicarbonates and citrates Solubility productSolubility product::

Ca++ x PO4--- = constantCa++ x PO4--- = constant

Increase in one leads to decrease in otherIncrease in one leads to decrease in other..

Bone cellsBone cells

11 - -Osteobalsts: Osteobalsts: bone-forming cellsbone-forming cells..

22 - -OsteocytesOsteocytes..

33 - -Osteoclasts: Osteoclasts: bone-eating cellsbone-eating cells..

Hormones involved in calcium homeostasisHormones involved in calcium homeostasisParathormoneParathormoneCalcitoninCalcitoninVitamin DVitamin D

SourceSourceParathyroidParathyroidParafollicular Parafollicular cells of thyroidcells of thyroid

SkinSkin

ActionsActions

11--On bonesOn bones

--Rapid phaseRapid phase::

OsteolysisOsteolysis..

--Slow phaseSlow phase::

InhibitsInhibits

activity of activity of osteoclastsosteoclasts

Remodeling of Remodeling of bonebone

22--On kidneysOn kidneys↑↑Ca & ↓PO4Ca & ↓PO4 reabsorption reabsorption by DCTby DCT..

Excretion of Excretion of both Ca & both Ca & PO4 in urinePO4 in urine

↑↑ reabsorption reabsorption of Ca from of Ca from DCT & PO4 DCT & PO4 from PCTfrom PCT

33--On GITOn GIT↑↑ reabsorption reabsorption of Ca indirectly of Ca indirectly by activating by activating Vitamin D3Vitamin D3..

↑↑ intestinal intestinal absorption of absorption of Ca & PO4Ca & PO4..

TetanyTetany

↑↑ neuromuscular excitability due to neuromuscular excitability due to ↑↑ ionized ionized

Ca causing increased neuronal permeabilityCa causing increased neuronal permeability

and clonic contractions of skeletal musclesand clonic contractions of skeletal muscles..

Causes of hypocalcemiaCauses of hypocalcemia::

- -HypoparathyroidismHypoparathyroidism..

- -Vitamin D deficiencyVitamin D deficiency..

- -AlkalemiaAlkalemia..

- -Renal failureRenal failure..

TetanyTetanyLatent tetanyLatent tetany::

Ca level is between 7-9 mgCa level is between 7-9 mg % %Spasm in certain parts of the body as Spasm in certain parts of the body as carpopedal spasm of the hands musclescarpopedal spasm of the hands muscles..Manifest tetanyManifest tetany::

Ca level drops below 7 mgCa level drops below 7 mg.%.%Spasmodic contractions of hands & feetSpasmodic contractions of hands & feet..

May die with asphyxia & cyanosis due to May die with asphyxia & cyanosis due to spasmodic contractions of laryngeal and spasmodic contractions of laryngeal and respiratory musclesrespiratory muscles..